This invention concerns door closers of the kind comprising an actuator assembly intended for concealed fitting within the thickness of a door, and an anchor member for fixing to a door frame, and in which an operating member is coupled to said anchor member and is movable within the actuator assembly under the action of driving means, usually comprising one or more mechanical springs, and under the control of a uni-directionally operative fluid-filled damper which serves to regulate the rate of movement of the door in the direction of closure without significantly restricting the rate of movement of the door in the direction of opening.
It is desirable for the action of any damper in such a door closer to be adjustable so as to enable the rate of closure to be set to fall within a chosen range despite variations in the weight and other parameters of different doors with which the closer may be used, and for the closer to provide an augmented closing force as the door reaches its closed position in order to overcome resistance from any latch fitted to the door.
GB 2 044 840 A discloses such a door closer, which comprises an actuating assembly which is disposed in a housing that is located within the thickness of the door, having an operating member which is movable linearly by means of one or more coil springs, and coupled by a flexible linkage to the anchor member which is attached to the door frame.
EP 0 016 445 A discloses a door closer of this type in which adjustment of the final part of the closure movement of the door is achieved by means of an adjustment member associated with the anchor member which is attached to the door frame, the adjustment member being disposed behind a mounting plate of the anchor member at a variable spacing so as effectively to adjust the length of the coupling between the anchor member and the operating member in the actuator assembly. This arrangement does not make any provision for adjustment of the overall rate of closure, but only in the final closure position of the door relative to a final part of the travel of the piston in the door-closing direction, in which final part of the travel the action of the damper is rendered ineffective so as to provide for a locally increased rate of closure movement to overcome any resistance which may be offered by a door latch for example.
Although the rate of movement of the door as it approaches its position of closure is increased, there is no provision for adjusting the driving force applied to the door over the final part of closure movement, as relieving the effect of the damper does not increase the force applied by the driving springs, but only allows the door to accelerate in response to the driving force and the closing action then relies on the momentum of the moving door to overcome latch resistance. However, the acceleration achieved depends on many variable factors, including the weight of the door, wind loading on the door, and frictional resistance in die hinges and in the latch itself etc., and accordingly such designs do not entirely address the problem of overcoming resistance associated with a door latch.
DE 1 708 349 A discloses a door closer having a main spring which acts over the full range of movement of a rod which is coupled by a link to and anchor member, and a supplementary spring arranged end to end with the main spring and effective to increase the driving force applied to the rod over the final part of the closure stroke, but without provision for varying the point at which the supplementary spring becomes effective.
Accordingly, it is an object of the present invention to make provision for an augmented closure force to come into play as the door approaches its position of closure, as compared with the force applied throughout the remainder of the range of movement, whilst providing for adjustment of the operation to suit a wide range of requirements not achieved previously.
According to a first aspect of the invention we provide a door closer comprising in combination:
an anchor member for mounting on a door frame,
an actuator assembly for mounting within the thickness of a door which is hinged for movement between open and closed positions relative to said door frame,
an operating member coupled by an articulated link to said anchor member and mounted in said actuator assembly for a range of movement between a retracted position in which said anchor member is held immediately adjacent to said actuator assembly and an extended position in which said anchor member is held in spaced relation to said actuator assembly,
resilient driving means arranged to exert a driving force on said operating member in a manner such as to drive said operating member towards said retracted position and thereby draw said anchor member and said actuator assembly together such that, when installed, the door closer acts to draw the door into its closed position relative to the frame,
a damper connected to said operating member so as to control the rate of movement of the operating member in at least a direction towards said retracted position, said damper comprising a cylinder containing hydraulic fluid, a piston rod carrying a piston which divides the cylinder into two chambers, and flow-restricting means to limit the rate of flow of hydraulic fluid flow one of said chambers to the other at least in one direction of fluid flow in response to movement of said operating member towards said retracted position, an adjustable throttle which comprises two elements in combination, the flow restriction imposed on the hydraulic fluid by said throttle being variable by relative positional adjustment of said two throttle elements, and an adjustment member to enable one of said throttle elements to be positionally adjusted relative to the other so as to vary the flow restriction imposed on the hydraulic fluid by said throttle,
resilient thrust means arranged to exert an increased driving force on said operating member, and
control means whereby said thrust means is operative to apply said increased driving force to said operating member over a defined part of said range of movement as said operating member approaches said retracted position, corresponding to movement of the door over the final part of its movement into its closed position, and
an adjustment member operatively connected with said control means to vary the point in the range of movement of said operating member at which said resilient thrust means becomes operative to apply said increased driving force.
The control means preferably includes a detent means arranged to hold the thrust means in a stressed condition over the whole of the range of movement of the operating means apart from said defined part thereof.
In one arrangement, the thrust means may include a compression spring located within a guide member which is coupled to said operating means and slidable therewith along a fixed shaft, and the detent means may be mounted on a carrier member which abuts one end of the compression spring and is slidable on said fixed shaft and located on this said guide member for limited movement longitudinally thereof, the detent means being engagable in an internal recess formed within said guide member to hold the compression spring in a compressed condition, and being displaceable from said internal recess to release said compression spring at a predetermined position along said shaft.
The detent means may be displaceable from said position of engagement with said internal recess in said guide member into a position of engagement with an external recess formed in said shaft to hold said carrier member in a predetermined position on said shaft. Preferably, the detent means comprises a plurality of balls located in one or more transverse bores formed in the carrier member, and each of said balls is of a diameter greater than the radial spacing between said shaft and said guide member so that said balls are either held by said shaft in said internal recess in said guide member or by said guide member in said external recess in said shaft.
In a particularly preferred arrangement, the bores in which the balls are located are formed with a radially inner portion having a diameter such as to accept the ball with a slight clearance and a radially outer portion having a greater diameter, the two portions of the bore meeting at an internal shoulder which is located at a spacing from the shaft which is less than the radius of the ball. With this arrangement when the ball is held in the internal recess of the guide member, it has been found that the ball does not bind on the shaft, thereby allowing the shaft to move freely relative to the carrier.
In a preferred arrangement the cylinder of the damper is moveable relative to the actuator assembly and the piston is static, and the flow restriction means is incorporated into said piston and piston rod, and the adjustment member has an operating element which is accessible from one end of said piston rod.
The adjustment member may comprise a shaft located within an axial bore formed in said piston rod, with an external threaded formation engaging an internal threaded formation in the bore of the piston rod whereby rotation of the shaft varies its axial position within said bore. The shaft may be provided at one end with a needle formation which comprises one of said throttle elements to cooperate with an orifice defined by the other of said elements, and at its other end with a head formation whereby the shaft may be rotated.
The thrust means may comprise one or more spring elements having a higher rate than the resilient driving means. Preferably both the driving means and the thrust means comprise one or more coiled compression springs, but other arrangements are possible. For example the thrust means may comprise one or more stacks of Belville washers, and the driving means could comprise gas-springs.
In a particularly convenient arrangement, said thrust means and said driving means each comprise two elements disposed symmetrically relative to a single damper means, but other arrangements are possible.